Process of treating combustible metallurgical-furnace gas to increase its calorific value.



H. L. DOHERTY. PROCESS OF TREATING GOMBUSTIBLE METALLURGICAL FURNACE GASTO INCREASE ITS CALORIFIG VALUE.

APPLICATION FILED FBB.17, 1910.

Patented Aug. 12, 1913.

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HENRY L. DOHERTY, OF NEW YORK, N. Y.

PROCESS OF TREATING COMBUSTIBLE METALLURGICAL-FURNACE GAS TO INCREASEITS CALORIFIC VALUE.

Application filed February 17, 1910.

T 0 all whom it may concern Be it known that I, I'IENRY L. Dorrnn'rr, acitizen of the United States, and a resident of New York city, in thecounty of New York and State of New York, have invented certain new anduseful Improvements in Processes of Treating CombustibleMetallurgical-Furnace Gas to Increase Its. Calorific Value, of which thefollowing is a specification.

This invention relates to a process of treating combustiblemetallurgical-furnace gas to increase its calorific value and, inparticular, to a process for accomplishing this end by reducing thecarbon dioxid in said gas to carbon monoxid.

The object of my invention is the increasing of the calorific value ofblast furnace gas, or other metallurgical furnace gas, by changing itscarbon dioxid to carbon monoxid, at the expense of what is, otherwise,practically waste heat of the blast furnace.

Briefly, my invention consists in withdrawing a portion of the gasgenerated in the furnace, preferably, at a Zone in the furnace such,that the cooling action to which the residual gases are subjected bycontact with the raw materials of the charge in the upper portion of thefurnace will be sufiicient to reduce their temperature to approximate aselected degree set forth below, and contacting the portion of thefurnace gases so withdrawn with incandescent carbon, together withvarious other features described in detail below. In the mostadvantageous form of my invention I pass the hot gases downward throughthe bed of fuel, whereby the hottest gases are contacted with thefreshest fuel which contains the greatest proportion of combustiblecarbonaceous material, and where the reduction of CO and IL0 is the mostrapid. As the gases pass downward. through the fuel bed, they are cooledby the absorption of their sensible heat to support the reducingreactions. They are thus, as their temperature falls, brought intocontact with fuel containing a regressively lower proportion ofcombustible and a progressively greater proportion of ash. As thetendency of the coked fuel and ash mixture to form clinker increaseswith the decrease in the ratio of combustible to ash, and thetemperature of the gases decreases with the decrease in carbon in thefuel with which they are in con- Specification of Letters Patent.

Patented A11 12,1913.

Serial No. 544,485.

tact, by regulating the temperature at which the gases are introducedinto the upper part of the fuel body, it is obviously possible toestablish, with fuels of normal composition, such a relation between thetemperature of the gases and the composition of the fuel body with whichthey are in contact, that the formation of clinker may be reduced to aminimum or almost entirely avoided.

In the accompanying drawings, I have shown a form of apparatus forapplying my invention.

Figure 1 is a diagrammatic elevation of my apparatus. Fig. 2 is avertical section through the carbon dioXid reducer or car bon mo'noxidgenerator and superheater of the .ame.

In the several views, 1 is the blast furnace in which the gas isgenerated as a necessary by-productof the smelting operation in thefurnace.

2 is the downcomer or gas conduit through which the gases are withdrawnfrom the furnace in normal operation.

3 is a conduit conducting to the carbon dioxid reducer or carbon monoxidgenerator 4, that portion of the furnace gas which I desire to treat forthe reduction of C0 5 is a bustle-pipe encircling 1 at a considerabledistance below the top of the furnace. A plurality of connections, 6,6", etc., establish communication between the bustle-pipe 5 and theinterior of the furnace 1. Dampers 7, 7", etc., on the respectiveconnections (3, (3, etc., permit of t e regulation of the volume of thehot gases withdrawn through the respective connections to secure auniform withdrawal of gases around the periphery of the furnace shaft. 3is connected, on the one hand, with the downcomer 2 by the connection 8,and on the other hand, with the bustle-pipe 5 by the connection 9.Valves or dampers 8 and 9, respectively, serve to regulate the relativeproportion of furnace gases withdrawn from the respective off-takes 2and 5 which go to the generator 4, or communication between 2 and 3 maybe cutoff entirely by valve 8".

The generator 4:, is built on the general lines of an ordinary gasproducer, with only such changes as are necessary, or at leastadvisable, to adapt it to carry out my process.

10 is the refractory wall of generator 4.

11 is a metal shell incasing the walls 1O.

12 is the thick arched top of generator 4, built of fireclay or otherrefractory material.

13 is the hopper bottom of the fuel chamber 14.

15, 15 are poke-holes in the arched top 12 of chamber 14, 15, 15poke-holes in the wall 11 which provide means of access to the fuelchamber 14 for the purpose of working the fuel bed in 14.

16 is the fuel charging opening, 17 the fuel hopper.

18 is the gascollecting chamber to which the gas passes on leaving thefuel bed 19 in chamber 14.

20 is the gas conduit conducting the enriched gas from the generator 4to the gas recuperator or cooler 21.

22 is a hopper Which receives the ash and unburned fuel discharged fromthe fuel bed 19 and guides it into the ash chute 23.

A horizontally-moving gate 24 provided with racks 25 and 25 is operatedby the shaft 26 bearing the spur wheels 27 and 27'. On opening the gate24, the ash drops into the ash pit 28 and, after closing gate 24, can beremoved through the ash door 29.

The gas to be treated is admitted to the upper part of the fuel chamber14, from the conduit 3.

The recuperator 21 may be of any type preferred. It is simply necessarythat the construction be such that the gas will be cooled down to atemperature that will not injure the exhauster 30. Usually it comprisesa number of fines through which the gas circulates and which are cooledby a current of air flowing in a direction opposite to that of the gas.The exhauster 30 may be of any type in common use, or which may bepreferred. The conduit 31 connects the recuperator 21 with the exhauster30. The discharge pipe 32 of exhauster 30, conducts the treated gas toany place of use desired.

The method of carrying out my invention in its most advantageous form isas fol.- lows :The gas to be treated is drawn off of the furnace 1through the connections 6, 6", etc., and passes through the bustle-pipe5 and conduit 3 to the generator of CO reducer 4. The proportion of gaswithdrawn through 6, etc., should be so regulated as not to interferewith the working of the furnace. The off-takes 6, etc., should belocated at that Zone of the furnace at which the gases will have duringthe coolest working that occurs in normal operation a temperature suchthat, after passing through the several conduits to the generator 4,they will enter the latter with suflicient sensible heat to sustain thereducing reaction which they undergo therein. All of the gas passages upto the generator 4 should have a heavy lining of fireclay, and beheavily insulated externally. The gas as it leaves the furnace willusually have a composition of, approximately,

Carbon monoxid:23% by volume, Carbon d1oX1d :12%

Hydrogen 2% Methane 2% Nater vapor 3% Nitrogen :58% ,7

(a) GOA-0:200.

I thus not only secure the elimination of CO from the gas but change itinto double the volume of a combustible gas. Since I am not, in thiscase, using air to malntain the temperature of the fuel bed Iamintroducing no additional nitrogen into the gas. The increase involume which l secure (equal to the original volume of the reducible COby thus changing the CO to GO thus reduces the proportion of nitrogen inan inverse ratio to one-half of the increase in relative volume of COpresent in the gas. The reduction in percentage of non-combustible,which I secure by my treatment of the furnace gas, is thus considerablygreater than that due to the volume of CO eliminated. A blast furnacegas of the composition given, after treatment under favorableCODClltlOl'lS, would have a composition as follows z- G0 38.4% 00 2.7%TL 3.8% 011,: 1.3% T1 0: 1.6% N :52.2%

The calorific value (latent) of the untreated gas of the compositiongiven would be 100 B. T. U. per cu. ft. (normal) while the treated gaswould have a calorific value of 148 B. T. U. per cu. ft. (normal). Atthe same time, the volume of the treated gas has been increased by 11.5%of the volume of the untreated gas. In other words, the latent calorificvalue per cu. ft. of the untreated gas has been increased by mytreatment to 165 B. T. U. per cu. ft. This is a very important pointwhere the blast furnace gas is to be used for the production of hightemperatures. The removal of the CO and the diminution in the percentageof nitrogen, with the proportionate increase in the carbon monoxid, willpermit of the attainment of much higher flame temperatures. Be-

sides, by withdrawing a portion of the from the furnace gases at a pointwell down in the stack, I can practically equalize the thermalcapacities of the descending charge of solid material and the ascendinggas current passing in contact therewith, thus securing a betterrecuperation of the sensible heat of the gases discharging through theregular downcomer. If, for any reason, it is not desirable to withdrawthe portion of the furnace gases that are to be passed through thegenerator, from the bustle-pipe 5, I then withdraw them from the maincurrent of gases passing through the downcomer 2. In this case it isusually necessary to supply additional sensible heat to the gases priorto passing them through the fuel bed in the reducer according to theprocess of my Letters Patent 964,901, dated July 19, 1910.

The temperature of the furnace gases, at any given level in the furnace,necessarily varies more or less according to the conditions of running.As stated, I prefer to locate the gas off-takes (5, 6, etc., at thatzone of the furnace at which the gases will have, during the coolestrunning, a sutiieiently high temperature to sustain the generatorreaction. In this case, during normal running, or abnormally hotrunning, the gases at the level of 6', 6, etc., will have a temperaturein excess of that required. Therefore, instead of withdrawing all of thegas to be treated from 6 and 6 I draw the gas in part from 6, 6", etc.,and in part from the top of the furnace through the conduits 2 and S,the two streams uniting and flowing through the conduit 3 to thegenerator 4-. By adjusting valves 8 and 9 and the speed of the exhausterit is obvious that any desired mixture of the two gases and thereforeany desired temperature may be secured in the gases introduced into thegenerator, between the temperature prevailing in the furnace at thelevel of 6 and 6 and that prevailing in the downcomer 2. Usually, theproportion of the gases drawn from the downcomer will be relativelysmall, since I use only sutlicient of the downcomer gases to balance anyexcess of temperature that may exist in the furnace gases at the levelof the off-takes 6, 6", etc.

When the furnace gas, for any reason, contains an abnormal percentage ofCO and it is not practicable to withdraw the gas at the propertemperature, or to communicate to the gas in the manner described in theLetters Patent mentioned sufficient heat to insure the reduction of theC0, of the gas in its passage through the fuel bed, I have recourse toanother method of heating the gas, which I prefer to employ as a purelyauxiliary method to the one of heating by means of the combustion of aportion of the gas .in the recuperator according to the said LettersPatent. In this auxiliary method, I pass into the upper part of thereducer above the fuel bed with the gas, a small proportion of air,preferably that which has been heated in the gas cooler or recuperator21 by the finished gas discharging from the generator 4. Thismodification, however, is disclosed and claimed in my Lettors Patent No.1,008,450, dated Nov. 14th, 1911, and I therefore do not describe it indetail herein.

By my preferred method of introducing the superheated gas to be treatedabove the fuel bed in the producer, the temperature that I may give tothe crude gas is limited only by the degree of refractoriness of thematerials used for the lining of the superheater, conduits andgenerator. The higher the temperature of the gases, within practicalworking limits, the more energetic is the reduction. Vith high initialtemperature therefore, the reduction is carried out, for the most part,in the upper strata of the fuel bed, and the gases, as they are cooledby the reactions, are brought into contact with a fuel body containing alessening proportion of combustible and an increasing proportion of ash.By regulating the initial. tempera ture, so that the temperature of thegases after the completion of the reactions shall not be above theclinker-ing temperature of the ash, it is thus possible to carry out thetreatment of the gases without the formation of an objectionable amountof clinker-s in the reducer. This method of operation thus permits thecontacting of the hottest gases with that portion of the fuel containingthe greatest proportion of combustible and then with fuel containing aregressively lessening proportion of combustible as the temperature ofthe gases diminishes. For this reason this method of operating thegenerator possesses decided advantages, although my process may becarried out in an ordinary up-draft producer of proper construction.

When the gas to be treated is introduced into the lower portion of a bedof fuel, in contact with the ash of the fuel, the temperature that maybe given to the entering gas is limited by the sintering temperature ofthe ash, and also, where the fuel bed is supported upon an ordinarygrate, by the temperature that the grate will stand. When thetemperature towhich the ash is exposed exceeds the sinteringtemperature, the result is that the ash is fused into an almost solidmass of clinker that may completely cut off the draft of the generator.When this occurs, it is of course necessary that the operations besuspended until the clinker formed has been removed. The necessity ofsuch an operation introduces such troublesome irregularities intreatment and in the quality of the gas produced that such a method ofoperating is almost impracticable. By my method of introducing thesuperheated gas above the fuel bed in contact with the latest chargedfuel I am able to enter the gas with suflicient contained heat tosustain the reactions in the generator and yet avoid any objectionableclinkering. The reason for this is that, in the first place, the freshfuel (so long as it is non-caking) may be exposed to any temperaturedesired without the formation of clinkers in the ash zone so long as thehigh temperature of the fresh fuel is not permitted to" extend down intothe ash zone, or the zone in which the proportion of ash isconsiderable. The ash forming mineral in the fuel is, for the most part,disseminated throughout the fuel in small particles which are envelopedby the carbon, and are thus isolated from each other. In this conditionthe fuel can be heated so that the ash forming particles may be fused toa liquid, without the formation of any clinker, so long as thetemperature of the mass is reduced sufliciently to again solidify themineral particles be fore their carbonaceous envelops have been burnedaway. in my process, the reactions set up in the fuel bed automaticallyreduce the temperature both of the gas current and of the fuel of thebed before the lower layers thereof have been reached. Both thedissociating reactions, mention-ed, viz.,

absorb large quantities of heat. Since I am to enter my crude gas at atemperature such that, after its CO andv H O have been reduced, theresulting temperature of the gases and of the fuel. bed in contacttherewith, will have been reduced to a point below the softening pointof the mineral and matter of the coal, I secure the necessary reductionin temperature of the partially consumed fuel before the carbonaceousenvelops of the ash-forming particles have been sufficiently burned awayto permit of the particles coming into mutual contact.

When the flame temperature that may be developed by the untreated gas,is sulficiently high to permit of the main current of furnace gas beinggiven the proper temperature to sustain the reaction in the generator Iuse the untreated gas for heating the superheater. When the untreatedgas will not develop the required temperature I then divert part of therich, treated gas back through the pipe 21 and connections to thesuperheater.

It is to be understood that my present invention may be appliedadvantageously to the treatment of gases from metallurgical furnacesgenerally which have a composition similar to that of blast furnace gas,viz., a larger content of oxygen (combined) in relation to the nitrogenpresent than exists in air.

Having described my invention, what I claim is:

1. The process of treating a combustible furnace gas containing carbondioXid, which consists in withdrawing the said gas from the furnace at atemperature such that the contained sensible heat of the gas will besufficient to balance the heat required for the dissociation of thereducible proportion of its carbon dioXid and passing the said gas incontact with ignited fuel, the said gas being first contacted withrelatively fresh fuel, whereby the reducible carbon dioXid of the gas isconverted to carbon monoxid.

2. The process of treating a combustible furnace gas containingreducible quantities of carbon dioxid which consists in withdrawing thesaid gas from the furnace at a temperature such that the containedsensible heat of the gas will be sufficient to balance the heat requiredfor the dissociation of the reducible proportion of its carbon dioxidand passing the said gas in contact with nited fuel, the said gas beingfirst contacted with that portion of the fuel containing the greatestproportion of combustible and then with fuel containing a regressivelyless proportion of combustible as the temperature of the said gas isdiminished by the heat absorbed in the reduction of its contained carbondioxid to carbon monoxid.

3. The process of treating a combustible furnace gas containing areducible proportion of carbon dioXid which consists in withdrawing thesaid gas from the furnace at a temperature such that the containedsensible heat of the gas will be sufficient to balance the heatabsorption in the reduction of its reducible carbon dioxid and passingthe said gas through the fuel bed of a downdraft producer.

t. The process of treating a combustible metallurgical-furnace gascontaining a reducible proportion of carbon-dioxid which consists inwithdrawing the said gas from the furnace at a temperature as near theone at which the sensible heat of the gas will suffice to balance theheat required for the reduction of its reducible carbon dioxid, as ispracticable, supplying any deficiency in the sensible heat of the gasbelow the quantity specified by burning a portion of said gas to heatthe remainder, and passing the hot furnace gas in contact withincandescent carbonaceous fuel whereby the reducible carbon dioxid ofsaid gas is reduced to carbon monoxid.

5. The process of treating a combustible metallurgical-furnace gascontaining a reducible proportion of carbon dioxid which consists inwithdrawing said gas from the furnace at a temperature as near to theone at which the sensible heat of the gas will sutlice to balance theheat required for the reduction of its reducible carbon dioxid, as ispracticable, supplying any deficiency in the sensible heat of the gasbelow the quantity specified by burning a portion of said gas to heatthe remainder, and passing the hot furnace in contact with incandescentcarbonaceous fuel, the said gas being first contacted with that portionof said fuel containing the greatest proportion of combustible and thenwith fuel containing a regressively less proportion of combustible asthe temperature of the said is diminished by the heat absorbed in thereduction of its contained carbon dioxid to carbon monoxid.

6. The process of treating a combustible metallurgical furnace gascontaining a reducible proportion of carbon dioxid to change said carbondioxid to carbon monoxid which consists in withdrawing the said gas fromthe metallurgical furnace in which it is formed as near to the one atwhich the sensible heat of the gas will. sufiice to balance the heatrequired for the reduction of its reducible carbon dioxid as ispracticable, supplying any deficiency in the sensible heat of the gasbelow the quantity specified, by burning a portion of said gas by airheated by heat taken from the treated gas, to heat the remainder of saidgas, and passing the so-heated furnace gas in contact with inca'descentcarbonaceous fuel, the said gas being first contacted with. thatportion of said fuel which contains the greatest proportion ofcombustible and then with fuel containing a regressirely lesseningproportion of combustible as the temperature of the said gas isdiminished by the heat absorbed in the reduction of its contained carbondioxid to carbon monoxid.

7. The process of treating a combustible metallurgical-furmuxe gascontaining a reducible proportion of carbon dioxid to change said carbondioxid to carbon monoxid, which consists in withdrawing the said furnacegas from the furnace at a temperature as near to the one at Which thesensible heat of the gas will sutfice to counterbalance the heatrequired for the deduction of its reducible carbon dioxid, as ispracticable, supplying any deficiency in the sensible heat of the gasbelow the quantity above specilied by burning a portion of the saidfurnace gas by air which has been preheated by heat taken from a portionof treated gas, in proximity to a bed of ignited carbonaceous fuel andpassing the gas mixture resulting from the partial combustion of saidgas through said bed of ignited carbonaceous fuel,

whereby the reducible carbon dioxid of such gas mixture is reduced tocarbon monoxid.

8. The process of treating a combustible metallurgical-furnace gascontaining a reducible proportion of carbon dioxid to change said carbondioxid to carbon monoxid which consists in withdrawing the said furnacefrom the furnace at a temperature as near to the temperature at whichthe sensible heat of the gas will suffice to counterbalance the heatrequired for the re duction of its reducible carbon dioxid, as ispracticable, supplying any deficiency in the sensible heat of the gasbelow the quantity of heat above specified, by burning a portion of thesaid furnace gas by air which has been preheated by heat taken from aportion of treated gas, in proximity to a bed of ignited carbonaceousfuel, and passing the gas mixture resulting from the partial combustionof said gas through said bed of ignited carbonaceous fuel, the said gasmixture being contacted first with that extremity of said fuel bed inwhich the fuel contains the greatest proportion of combustible and thenwith fuel containing a regressivcly lessening proportion of combustibleas the temperature of the said gas is diminished by the heat absorbed inthe reduction of its contained carbon dioxid to carbon monoxid.

9. The process of treating a combustible metallurgical-furnace gas,containing a reducible proportion of carbon dioxid, to change saidcarbon dioxid tocarbon monoxid which consists in withdrawing the sailfurnace gas from the furnace at a temperature as near to thetei'nperature at which the sensible heat of the will suffice to sensibleheat of the gas below the quantity of heat above specified, by burning aportion of the said furnace gas by air, which has been preheated by heattaken from a portion of treated gas, in proximity to a bed ofcarbonaceous fuel, passing the gas mixture resulting from the partialcombustion of said gas through said bed of ignited carbonaceous fuel,the said gas mixture being contacted first with that extremity of saidfuel bed in which the fuel contains the greatest proportion ofcombustible and then with fuel containing a regressively lesseningproportion of combustible, as the temperature of the said gas isdiminished by the heat absorbed in the reduction of its contained carbondioxid to carbon monoxid, and passing the so-treated gas through arecuperator whereby a portion of the sensible heat of the treated gas istransferred to an air current.

10. The process of treating a combustible metalhirgical-furnace gas,containing a reducible proportion of carbon dioxid to balance of anysuch deficiency in the sen-.

sible heat of said gas by burning a portion of the remainder of said gasby admixing therewith in proximity to a mass of incandescentcarbonaceous fuel by air which has been preheated by heat taken from thesensible heat of a portion of finished gas, and contacting the gasmixture resulting from the above mentioned partial combustion of the gaswith said mass of incandescent carbonaceous fuel the said gas mixturebeing first contacted with that portion of said carbonaceous fuel havingthe highest proportion of combustible and then with fuel con taining aregressively lessening proportion of combustible, as the temperature ofsaid gas mixture is diminished by the heat absorbed in the reduction ofits contained carbon dioxid.

11. The process of treating a combustible metallurgical-furnace gascontaining a reducible proportion of carbon dioxid, to change saidcarbon dioxid to carbon monoxid which consists in withdrawing the saidfurnace gas from the furnace at a temperature as near to the temperatureat which the sensible heat of the gas will suffice to counterbalance theheat required for the reduction of its reducible carbon dioxid as ispracticable, supplying a portion of any deficiency in the sensible heatof the gas below the quantity of heat above specified, by burning aportion of said gas in a superheater to heat the remainder of said gas,supplying the bal ance of any such deficiency in the sensible heat ofsaid gas by burning a portion of the remainder of said gas in proximityto a mass of incandescent carbonaceous fuel by admixing with said gasthe pro-per proportion of preheated air, passing the resulting gaseousmixture in contact with said incandescent carbonaceous fuel the saidgaseous mixture being first contacted with that portion of said fuelcontaining the greatest proportion of combustible, and then withportions of said fuel containing a regressively lessening proportion ofcombustible, as the temperature of said gaseous mixture is diminished bythe heat absorbed in the reduction of its carbon dioxid and passing theso-treated gas through a recuperator whereby a portion of its sensibleheat is transferred to the air to be used in the heating of a freshportion of furnace gas.

Signed at New York city in the county of New York and State of New Yorkthis 16th day of February A. D. 1910.

HENRY L. DOHERTY. Witnesses V. G. BERRYMAN, THOS. I. CARTER.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. C.

